How to force AI to siege your cities

[Connacht]

For role-playing purpose, I often tried to force enemy armies to lay siege to my cities, defended by a punch of men. But I never accomplished my goal, even by leaving the city _undefended_ (it's a nonsense that a full stack enemy army would turn and go away if there is a city without any garrison nearby, imho).

I would like to know how to force AI to siege a city in order to fight particular battles. I would like to know this also for the eleutheroi because sometimes simply leaving a city with a low public order crashes the game because it tries to give the city to a vanquished faction, instead to rebels.

EDIT: I don't want to use fd and give the city to the enemy, since these are other cases in which my purpose is to fight particular siege battles with particular conditions and particular units for both sides (and also because giving the city with a diplomat spawns enemy units).